Previously, mechanical valves for shutting off fluid flow due to earthquakes have used the principle of falling objects either filling a valve seat or triggering a spring loaded secondary apparatus.
Pazmany in U.S. Pat. No. 4,091,831 teaches such a device with a ball mounted on a pedestal falling and rolling onto a seat when motivated by a seismic shock. U.S. Pat. No. 3,747,616 issued to Lloyd also uses a ball balanced on an inclined bar with a saddle similarly being unseated and falling into the valve inlet orifice, restricting the fluid flow.
A ball is also utilized in U.S. Pat. No. 3,768,497 of Mueller, wherein the ball falls onto a plate attached with a hinge to a closure diaphram shutting off the flow. Yamada in U.S. Pat. No. 3,878,858 teaches a ball on a pedestal falling to a secondary structure, triggering a valve, or the like.
Greer in U.S. Pat. No. 4,116,209 employs a plumb valve body with a groove in a merging corner supported by a rib, which is dislodged by seismic vibrations falling into the port of the valve, effectively blocking the fluid flow. U.S. Pat. No. 3,965,917 of Speck applies a pair of reactant masses moving into an in-line interlocking position, releasing a hinged arm containing a seat disc accomplishing the restriction. Similarly, in U.S. Pat. No. 3,791,396 Nelson exercises a balanced weight falling from a support assembly, triggering a spring loaded mechanism rotating a valve in a pipe line.
In each example of prior art, an object was dislodged from a stationary element, causing a reaction ultimately closing the valve, therefore, the action is dependant upon the mechanical positioning or angular displacement of the member to produce the desired sensitivity to a seismic shock wave.